A simple LED driver with low dimming switch stress

Abstract

This paper aims to investigate the low dimming switch stress of a light-emitting diode (LED) driver. Most dimmable LED drivers contain a series dimming switch with a LED string to implement a pulse-width modulation-dimming function. However, this setup causes the dimming switch to suffer from high voltage stress in the dimming interval. To reduce the voltage stress of a dimming switch, a low switch stress scheme is presented. The dimming circuit is parallel with the LED string. Using proper arrangement and design of the parameters, the dimming circuit changes the feedback status, which results in the output driving voltage varying between a constant current and a fixed voltage operation. These two operating conditions also make the LED string turn on/off alternately and consequently and perform the dimming function. The dimming switch acts by altering the feedback path instead of cutting off the main power flow; hence, it does not need a power level switch. Details of the operating principles and design considerations are discussed in this study. A prototype boost converter was developed to verify the feasibility of the proposed low dimming switch stress LED driver.

Single‐stage triple‐output Cuk power factor correction converter

“…During half line cycle, the maximum peak current of L 1 and L 2 occurs when ωt is π/2. Therefore, according to (1), ( 2), (13), and ( 16), the maximum peak current i L1,p_Max of L 1 during half line cycle can be given as…”

“…11 High power LED are gradually replacing traditional incandescent lamps and cold-cathode fluorescent lamps in general lighting applications because of these obvious advantages of high luminous efficiency, long life span, more environmentally friendly, excellent flexibility of brightness, and color control. 12,13 For those high-power LED power supply applications of multichannel LED strings, multiple-output current sources are needed to control precisely the forward current of each LED string and to avoid the current imbalance issue. 6,10,14 Most of multiple-output AC-DC LED drivers consist of two-stage converters.…”

Simplified electrical modelling of power LEDs for DC–DC converter analysis and simulation

“…Nowadays, power light emitting diodes (LEDs) are a good alternative for many lighting applications, because they have a high luminous efficiency and a long useful life. Therefore, several dc-dc converters have recently been proposed to feed power LEDs [1][2][3][4][5][6]. The simulations of these systems must be carried out with a reliable LED model so that the complete system behaviour can be investigated [7][8][9][10][11][12][13][14].…”

A long lifetime passive LED driver with power factor correction

“…Normally, a LED driver needs an ac-dc converter to convert the grid ac voltage to a low dc voltage. Although one can use an active power factor corrector (PFC) to achieve almost unity power factor easily [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], the added extra control circuit and the auxiliary power supply will not only increase the circuit complexity but also reduce the driver reliability. Although one can use an active power factor corrector (PFC) to achieve almost unity power factor easily [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], the added extra control circuit and the auxiliary power supply will not only increase the circuit complexity but also reduce the driver reliability.…”

“…According to Energy Star SSL requirement [5,6], the corresponding power factor at the ac side of the converter should be greater than 0.9 for commercial application and no less than 0.7 for residential application. Although one can use an active power factor corrector (PFC) to achieve almost unity power factor easily [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], the added extra control circuit and the auxiliary power supply will not only increase the circuit complexity but also reduce the driver reliability. Particularly, for outdoor lighting applications, the driver must be highly reliable to minimize the corresponding maintenance cost.…”